blob: 34c6fb31fa31c26ca1410cb2f28039b734031d7c [file] [log] [blame]
// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
// Tests local inference errors for the `in` variance modifier.
// SharedOptions=--enable-experiment=variance
class Covariant<out T> {}
class Contravariant<in T> {}
class Exactly<inout T> {}
class Upper {}
class Middle extends Upper {}
class Lower extends Middle {}
class ContraBound<in T> {
ContraBound(T x, void Function(T) y) {}
}
Exactly<T> inferCovContra<T>(Covariant<T> x, Contravariant<T> y) => new Exactly<T>();
Exactly<T> inferContraContra<T>(Contravariant<T> x, Contravariant<T> y) => new Exactly<T>();
Exactly<T> inferContraBound<T>(ContraBound<T> x) => new Exactly<T>();
main() {
Exactly<Upper> upper;
Exactly<Lower> lower;
// T <: Upper and T <: Middle.
// We choose Middle.
var inferredMiddle = inferContraContra(Contravariant<Upper>(), Contravariant<Middle>());
upper = inferredMiddle;
// ^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
// [cfe] A value of type 'Exactly<Middle>' can't be assigned to a variable of type 'Exactly<Upper>'.
// T <: Upper and T <: Lower.
// We choose Lower.
var inferredLower = inferContraContra(Contravariant<Upper>(), Contravariant<Lower>());
upper = inferredLower;
// ^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
// [cfe] A value of type 'Exactly<Lower>' can't be assigned to a variable of type 'Exactly<Upper>'.
// int <: T <: String is not a valid constraint.
inferCovContra(Covariant<int>(), Contravariant<String>());
//^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.COULD_NOT_INFER
// [cfe] unspecified
// String <: T <: int is not a valid constraint.
inferCovContra(Covariant<String>(), Contravariant<int>());
//^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.COULD_NOT_INFER
// [cfe] unspecified
// Middle <: T <: Lower is not a valid constraint
inferCovContra(Covariant<Middle>(), Contravariant<Lower>());
//^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.COULD_NOT_INFER
// [cfe] unspecified
// Upper <: T <: Lower is not a valid constraint
inferCovContra(Covariant<Upper>(), Contravariant<Lower>());
//^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.COULD_NOT_INFER
// [cfe] unspecified
// Upper <: T <: Middle is not a valid constraint
inferCovContra(Covariant<Upper>(), Contravariant<Middle>());
//^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.COULD_NOT_INFER
// [cfe] unspecified
// Inference for Contrabound(...) produces Lower <: T <: Upper.
// Since T is contravariant, we choose Upper as the solution.
var inferredContraUpper = inferContraBound(ContraBound(Lower(), (Upper x) {}));
lower = inferredContraUpper;
// ^^^^^^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
// [cfe] A value of type 'Exactly<Upper>' can't be assigned to a variable of type 'Exactly<Lower>'.
// Inference for Contrabound(...) produces Lower <: T <: Middle.
// Since T is contravariant, we choose Middle as the solution.
var inferredContraMiddle = inferContraBound(ContraBound(Lower(), (Middle x) {}));
lower = inferredContraMiddle;
// ^^^^^^^^^^^^^^^^^^^^
// [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
// [cfe] A value of type 'Exactly<Middle>' can't be assigned to a variable of type 'Exactly<Lower>'.
}